The present invention relates generally to photoelectric imaging devices and, more particularly, to a photoelectric imaging device adapted to use an external light source to illuminate the object being imaged.
Photoelectric imaging devices are well known in the art and produce machine-readable data representative of an object which is imaged, e.g., a page of printed text. One type of photoelectric imaging device is an optical scanning device. In an optical scanning device, an object is moved relative to the optical scanning device or visa versa as the optical scanning device generates data representative of the object. The data generated may be in the form of binary numbers and stored in a data storage device for processing. The following patents which describe optical scanners are hereby incorporated by reference for all that is disclosed therein: U.S. Pat. No. 5,552,597 of McConica for HAND-HELD SCANNER HAVING ADJUSTABLE LIGHT PATH; U.S. Pat. No. 5,646,394 of Steinle for IMAGING DEVICE WITH BEAM STEERING CAPABILITY; and U.S. Pat. No. 5,680,375 of Cristie et al. for ULTRAPORTABLE SCANNER.
Some photoelectric imaging devices employ line-focus systems, which image an object by sequentially focusing narrow xe2x80x9cscan linexe2x80x9d portions of the object onto a linear photosensor array. Examples of photoelectric imaging devices that use line-focus systems include optical scanning devices and facsimile machines. Scanning is performed by illuminating the object and focusing a line portion of the light reflected from the object onto the photosensor array. The narrow strip or line portion of the object which is imaged on the linear photosensor array is usually called a xe2x80x9cscan line.xe2x80x9d As the object is moved relative to the photoelectric imaging device, a plurality of scan line images are formed, which taken collectively, represent the object.
A photosensor array generally consists of a linear array of photodetector elements (or simply photodetectors), which correspond to small area locations on the scan line. These small area locations on the scan line are commonly referred to as xe2x80x9cpicture elementsxe2x80x9d or xe2x80x9cpixels.xe2x80x9d The corresponding photodetectors themselves are also sometimes referred to as pixels. In response to light from its corresponding pixel location on the scan line, each photodetector in the photosensor array produces a data signal which is representative of the light it experiences during an interval of time known as a sampling interval. The data signals from the photodetectors may be received and processed by an appropriate data processing system.
Monochrome optical scanners generate machine-readable data corresponding to a single monochrome image of the object being scanned. A monochrome scanner may, for example, generate a xe2x80x9cblack and whitexe2x80x9d image of a scanned object regardless of the actual colors contained in the object. In a color, or polychrome, optical scanner, machine-readable data is generated corresponding to a plurality of monochrome components (typically, red, green and blue) appearing in the object. Generally, the monochrome components are combined to arrive at a polychrome (color) image of the object.
Several methods for accomplishing color optical scanning are known in the art. One such method, known as a xe2x80x9cmulti-passxe2x80x9d scanning method, involves scanning the object several times. On the first xe2x80x9cscanning passxe2x80x9d, monochrome scan line images of the object corresponding to a single color (e.g., red) are impinged onto a single linear photosensor array. On the second scanning pass, monochrome scan line images are acquired which correspond to a second color (e.g., blue). The process is then repeated until the desired number of monochrome images of the object has been acquired. Thereafter, a computer processor may be used to combine the individual monochrome images into a polychrome image of the object. In some multi-pass scanning devices, the light source may be manipulated to provide the desired color of monochrome light during each scanning pass in order to select the color of the monochrome image which is acquired during each pass. In other multi-pass scanning devices, a plurality of filters may be selectively placed between the object and the photosensor array in order to select the color during each pass.
Another method for accomplishing color optical scanning is known as a xe2x80x9csingle passxe2x80x9d scanning method. In single pass color scanning, a plurality of linear photosensor arrays (e.g., three) may be used. Each of the photosensor arrays receives light of a different color (e.g., red, green and blue). In this manner, all of the desired monochrome images of the object may be acquired in a single scanning pass. Each of the linear photosensor arrays may be provided with a filter to cause the desired color of light to be impinged on the array. Alternatively, an optical beam splitting device may be used to separate light from the object being scanned into a plurality of monochrome components. Examples of optical scanning devices using such beam splitting devices are disclosed in the following U.S. Pat. No. 5,410,347 of Steinle et al. for COLOR OPTICAL SCANNER WITH IMAGE REGISTRATION HOLING ASSEMBLY; U.S. Pat. No. 4,870,268 of Vincent et al. for COLOR COMBINER AND SEPARATOR AND IMPLEMENTATIONS; U.S. Pat. No. 4,926,041 of Body for OPTICAL SCANNER (and corresponding EPO patent application no. 90306876.5 filed Jun. 22, 1990) U.S. Pat. No. 5,032,004 of Steinle for BEAM Splitter APPARATUS WITH ADJUSTABLE IMAGE FOCUS AND REGISTRATION (and corresponding EPO patent application no. 91304185.1 filed May 9, 1991); U.S. Pat. No. 5,044,727 of Steinle for BEAM Splitter/COMBINER APPARATUS (and corresponding EPO patent application no. 91303860.3 filed Apr. 29. 1991); U.S. Pat. No. 5,040,872 of Steinle for BEAM Splitter/COMBINER WITH PATH LENGTH COMPENSATOR (and corresponding EPO patent application no. 90124279.2 filed 12/14/90 which has been abandoned); and 5,227,620 of Elder, Jr. et al. for APPARATUS FOR ASSEMBLING COMPONENTS OF COLOR OPTICAL SCANNERS (and corresponding EPO patent application no. 91304403.8 filed May 16, 1991), which are all hereby incorporated by reference for all that is disclosed therein.
There are many types of photosensor devices known in the art. Two types of photosensor devices, however, are commonly used in optical scanning devices. These are the charged coupled device and the contact image sensor. A charged coupled device-type photosensor device is typically a single semiconductor chip with at least one linear array of photodetectors mounted to it. The semiconductor chip is typically much smaller than a desired scan line, so the image of the object must be focused onto the charged coupled device. For this reason, optical scanners using charged coupled devices typically require an extended focal length between the object being imaged and the charged coupled device.
A contact image sensor-type photosensor device is typically a linear arrangement of linear optical arrays. Each linear optical array has at least one linear array of photodetectors mounted to it. One example of a commercially available linear optical array used in a contact image sensor-type photosensor device is available from Texas Instruments, Inc. of Austin, Tex. and sold as model number TSL2301. The linear optical arrays are in close proximity to a lens, which in turn is in close proximity to the object being scanned. The lens typically has a reduction ratio of 1:1. An example of such a lens is the SELFOC lens manufactured by Mirco Optics Company, Limited, a subsidiary of the Nippon Sheet Glass, Limited. SELFOC is a registered trademark of Nippon Sheet Glass, Limited.
The lens receives light reflected from the object and focuses a scan line of the object onto the array of photodetectors. The photodetectors, in turn, output electrical data corresponding to the light they receive. The data from the photodetectors may be processed by a computer as is known in the art. Due to the 1:1 lens ratio, the length of a contact image sensor array of photodetectors may be substantially the same length as the scan line. Accordingly, an extended focal path, as described above with respect to a charged coupled device-type scanner, is not needed in a scanning device using a contact image sensor. An example of a contact image sensor device is disclosed in the U.S. patent Ser. No. 09/120,669 of Kochis et al. for MULTI-SEGMENT LINEAR PHOTOSENSOR ASSEMBLY, filed on Jul. 22, 1998, which is hereby incorporated by reference for all that is disclosed herein.
As computers and processing equipment have become smaller and less expensive, attempts have been made to make scanning devices more portable and less expensive. Improving portability includes making a scanning device which is easily transportable in that it is light weight, small, and uses minimal power. Likewise, optical systems for portable scanning devices must generally be very compact and light weight due to the constraints of their operation. The cost, size and weight of optical scanning devices may be reduced by limiting the number of components that are required to operate the optical scanning devices.
Conventional optical scanning devices require various onboard components in order to operate properly. These components include a light source, various optical components, including at least one photosensor device, a power source, a processor, a data storage device, and function buttons. The need for a light source dictates that a power source be provided to supply the light source. The processor is required to read the data from the photosensor device, convert the data to a form that may be read by a machine, and store the data in the data storage device. Function buttons may also be required as a user interface between the user and the optical scanning device.
The power source requirements and the internal devices required to operate optical scanning devices limit portability and increase the cost of optical scanning devices. The power source requirements and internal devices add bulk, weight, and expense to the optical scanning devices. The power source requirements also necessitate that optical scanning devices be operated in close proximity to an electrical source or be provided with batteries. If optical scanning devices are operated from an electrical source, such as an electrical outlet, the electrical source must be converted to a voltage which will operate the scanning electronics. Adding a voltage converter to an optical scanning device adds further weight, bulk and expense to the optical scanner. Batteries may be used to operate the light source and processing electronics; however, batteries are generally heavy, expensive, and require recharging or replacing.
Therefore, it would be generally desirable to provide a photoelectric imaging device that requires fewer onboard components and, thus, overcomes the aforementioned problems associated with photoelectric imaging devices.
The present invention is directed to an improved photoelectric imaging device which does not require an onboard light source. The improved photoelectric imaging device is configured to utilize light from an external source to illuminate the object being imaged. The external light source may be a linear source, such as a tube-shaped lamp, or it may be a planar source, such as a video display used with a desktop or laptop computer. The improved photoelectric imaging device, thus, does not require either a light source or an associated power source to be physically located within the photoelectric imaging device.
One application of the improved photoelectric imaging device is in an optical scanning device. The following description summarizes the improved photoelectric imaging device as used in an optical scanning device. It is to be understood, however, that the improved photoelectric imaging device is applicable to other types of imaging devices as well.
The improved scanning device is configured to collect light from an external light source in order to illuminate the object which is to be scanned. The configuration of the scanning device may be such that light from the external source enters the bottom of the scanning device and travels through the scanning device to illuminate the object, which may be located on top of the scanning device. In one embodiment, the scanning device may be configured to focus light from a video display onto the object which is to be scanned, thereby using the video display as the external light source.
The external light source may be operated to provide a light source for either a monochrome or a polychrome scan. In the case of monochrome scanning, the external light source may, for example, emit either white or green light to illuminate the object to be scanned. In the case of polychrome scanning, the external light source may emit a full spectrum of light necessary to image the colors in the object, e.g., red, green, and blue spectral components.
The external light source may emit light over an area that is wide enough to illuminate the object, and thus, may be adequately used to illuminate a scan line on the object. Light reflected from the illuminated object may then be focused onto a photosensor device located in the scanning device. The photosensor device may then convert the reflected light to electrical data for processing.
During a scan, the object to be imaged may be passed over an illumination area on the scanning device. As the object is passed over the illumination area of the scanning device, light from the external light source illuminates the object. The reflected light from the illuminated object, in the form of a scan line, is focused onto the photosensor device. As scanning occurs, the accrual of scan lines may be processed and stored by an external computer, eliminating the need for an onboard processor located within the scanning device. Alternatively, the data processing and storage may be performed by a processor that is internal to the scanning device.
The improved scanning device may be made particularly portable and economical when the external light source is a video display as used with an external computer. In this case, no light source is required to be located within the improved scanning device and, therefore, no power supply for the light source is required to be located within the improved scanning device. The improved scanning device may further use the external computer to process the image data, further decreasing the weight, size, cost and complexity of the improved scanning device by eliminating the need for a complex processor and a data storage device to be located within the improved scanning device. The external computer may also control the spectral components emitted by the video display.